Mr . Macartney's Observations 
290 
operate on the luminous matter (while in the living body.) 
only indirectly, by exciting the animal. — The luminous matter, 
in all situations, so far from possessing phosphoric properties, 
is incombustible, and loses the quality of emitting light, by 
being dried, or much heated. — The exhibition of light, how- 
ever long it may be continued, causes no diminution of the 
bulk of the luminous matter. It does not require tne presence 
of pure air, and is not extinguished by other gasses. 
The luminous appearance of living animals is not exhausted 
by long continuance, or frequent repetitions, nor accumulated 
by exposure to natural light ; it is therefore, not dependent 
upon any foreign source, but inheres as a property, in a pe- 
culiarly organized animal substance or fluid, and is regulated 
by the same laws which govern all the other functions of 
living beings. 
The light of the sea is always produced by living animals, 
and most frequently by the presence of the medusa scintillans. 
When great numbers of this species approach the surface, they 
sometimes coalesce together, and cause that snowy or milky 
appearance of the sea, which is so alarming to navigators. 
These animals, when congregated on the surface of the 
water, can produce a flash of light, somewhat like an electric 
corruscation. When the luminous medusae are very nume- 
rous, as frequently happens in confined bays, they form a 
considerable portion of the mass of the sea, at which times 
they render the water heavier, and more nauseous to the taste ; 
it is therefore adviseable to always strain sea water before 
it is drunk. 
The luminous property does not appear to have any con- 
nection with the oeconomy of the animals that possess it, 
